lol, Thanks :).
From Wikipedia:
"Informally, especially in computer science, the Big O notation often is permitted to be somewhat abused to describe an asymptotic tight bound where using Big Theta Θ notation might be more factually appropriate in a given context."

As far as I understand this solution is O(nm).
Where n is the length of a and m is the length of b.
It is not O(n^2), unless you're assuming a and b must be the same length?
If a.length is 100 and b.length is 1, the number of comparisons is 100, not 10,000...